Abstract : ENTAL STUDY OF THE PRE-BUCKLING AND POSTBUCKLING BEHAVIOR OF THIN ALUMINUM CYLINDRICAL SHELLS WITH R/h of 100 under a pure applied torque is reported. The investigation includes initially-undamaged and pre-damaged cylindrical shells. The types of predamage include a single circular 1-inch diameter hole, and a single size rectangular slot (3/8-inch wide and 2.10-inch long) with orientations of 0, 45, and 90 degrees to the longitudinal axis of the cylindrical shell. Postbuckling behavior of these specimens is investigated for large twist angles, for both monotonically-increasing angular deflections and for unloading-reloading behavior. Load-deflection characteristics and buckling patterns distinctive to each type of specimen tested are presented. Finally, comments are offered on idealizing these buckling patterns for possible use in the future development of approximate methods for predicting these types of postbuckling load-deflection behavior. (Author)